1. Field of the Invention
This invention relates generally to semiconductor processing, and more particularly to waffle packs to hold semiconductor die and to methods of using the same.
2. Description of the Related Art
Many current integrated circuits are formed as multiple die on a common wafer. After the basic process steps to form the circuits on the die are complete, the individual die are cut from the wafer. The cut die are then usually mounted to structures, such as circuit boards, or packaged in some form of enclosure.
One frequently-used package consists of a substrate upon which a die is mounted. The upper surface of the substrate includes electrical interconnects. The die is manufactured with a plurality of bond pads. A collection of solder bumps are provided between the bond pads of the die and substrate interconnects to establish ohmic contact. After the die is mounted to the substrate, a lid is attached to the substrate to cover the die. Some conventional integrated circuits, such as microprocessors, generate sizeable quantities of heat that must be ferried away to avoid device shutdown or damage. The lid serves as both a protective cover and a heat transfer pathway.
Before packaging, the cut die are provided with solder bumps and thereafter subjected to some form of visual inspection to verify that the solder bumps meet specifications. Accordingly, the die are positioned bump-up so that the bumps can be observed. After visual inspection, the die must be flipped over for flip-chip mounting on a substrate.
One conventional way of handling the cut die after bump deposition involves the use of a conventional single-sided waffle pack. The conventional waffle pack consists of a body that has a plurality of die-shaped cavities on one side and a large cavity on the opposite side. In the conventional method, die are loaded into the cavities bump-side up and a visual inspection is performed. In order to prepare for packaging, the die must next be flipped over to a bump-side down position. This entails flipping over an empty single-sided waffle pack and placing it on the loaded waffle pack. The inverted and upright waffle packs are not natively designed to mate up so a flipping jig is used to provide axial alignment. With the flipping jig in place, the inverted and upright waffle packs are lifted and flipped over. The flipping jig is removed and the formerly underlying upright waffle pack is lifted off to expose the die. A machine is then activated to lift out the bump-side down die and transport them for flip-chip mounting.
The difficulty with this method is that each loaded waffle pack must be flipped one at a time. Thus, the throughput is somewhat limited. Even with a flipping jig, axial alignment is sometimes imperfect. If there is misalignment between the inverted waffle pack and the loaded waffle pack, the die may jostle about as the stack is flipped, resulting in smearing or other damage to the solder bumps.
The present invention is directed to overcoming or reducing the effects of one or more of the foregoing disadvantages.